Proteins are the building blocks of life and every living cell uses them for both structural and functional purposes.

They are long chains of amino acids linked together like beads on a string, then folded into complex shapes.

There are 9 essential amino acids that you must get through your diet, and 12 that are non-essential, which your body can produce from other organic molecules.

The quality of a protein source depends on its amino acid profile. The best dietary sources of protein contain all essential amino acids in ratios appropriate for humans.

In this regard, animal proteins are better than plant proteins. Given that the muscle tissues of animals are very similar to those of humans, this makes perfect sense.

The basic recommendations for protein intake are 0.36 grams of protein per pound of body weight (0.8 grams per kg) daily. This translates to 56 grams of protein for a 154-pound (70-kg) individual (1).

This meager intake may be enough to prevent downright protein deficiency. Yet, many scientists believe it’s not sufficient to optimize health and body composition.

People who are physically active or lift weights need a lot more than that. Evidence also shows that older individuals may benefit from a higher protein intake (2, 3).

For detailed information on how much protein you should get per day, check out this article.

Summary Protein is an essential macronutrient. Although the recommended daily intake may be enough to prevent deficiency, some scientists believe it’s insufficient to optimize health and body composition.

Some people believe that a high protein intake can contribute to osteoporosis.

The theory is that protein increases the acid load of your body, which then causes the body to take calcium out of the bones to neutralize the acid (4).

Even though there are some studies showing increased short-term calcium excretion, this effect does not persist over the long term (5).

In fact, longer-term studies do not support this idea. In one 9-week study, replacing carbohydrates with meat did not affect calcium excretion and improved some hormones known to promote bone health, like IGF-1 (6).

A review published in 2017 concluded that increased protein intake does not harm the bones. If anything, the evidence pointed to a higher protein intake improving bone health (7).

Multiple other studies show that a higher protein intake is a good thing when it comes to your bone health.

For example, it may improve your bone density and lower the risk of fractures. It also increases IGF-1 and lean mass, both known to promote bone health (8, 9, 10, 11).

However, if we eat more than we need, the excess protein will be broken down and used for energy.

Even though a relatively high protein intake is healthy and safe, eating massive amounts of protein is unnatural and may cause harm. Traditional populations got most of their calories from fat or carbs, not protein.

Exactly how much protein is harmful is unclear and likely varies between people.

One study in healthy, strength-training men showed that eating around 1.4 grams per pound of body weight (3 grams per kg) every day for a year didn’t have any adverse health effects (12).

Even eating 2 grams of protein per pound of body weight (4.4 grams per kg) for 2 months did not appear to cause any side effects (25).

But keep in mind that physically active people, especially strength athletes or bodybuilders, need more protein than less active individuals.

Summary Extremely high protein intake is unhealthy. It is unclear at what intake level protein becomes harmful. It likely depends on the individual.